问题：
最近一直被这个问题困扰 zabbix 点击用户标签后就卡住了，这个zabbix安装到现在2年多的时间。
如下图，
解决方案：
删除 sessions表中的记录
sessions 表很重要，保存了每个用户的sessions,在登陆、注销的时候均会操作
该张表的。
登陆数据库：
[root@zabbixmysql ~]# mysql -uroot -p
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 158608484
Server version: 5.7.18-log MySQL Community Server (GPL)
Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql>
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| haiwai_zabbix |
| mysql |
| percona_schema |
| performance_schema |
| sys |
| zabbix |
| zabbix_proxy |
| zabbix_server |
| zabbix_test |
+--------------------+
10 rows in set (0.06 sec)
mysql> use haiwai_zabbix;
mysql> show tables;
+----------------------------+
| Tables_in_haiwai_zabbix |
+----------------------------+
| acknowledges |
| actions |
| alerts |
| application_discovery |
| application_prototype |
| application_template |
| applications |
| auditlog |
| auditlog_details |
| autoreg_host |
| checksums |
| conditions |
| config |
| corr_condition |
| corr_condition_group |
| corr_condition_tag |
| corr_condition_tagpair |
| corr_condition_tagvalue |
| corr_operation |
| correlation |
| dbversion |
| dchecks |
| dhosts |
| drules |
| dservices |
| escalations |
| event_recovery |
| event_tag |
| events |
| expressions |
| functions |
| globalmacro |
| globalvars |
| graph_discovery |
| graph_theme |
| graphs |
| graphs_items |
| group_discovery |
| group_prototype |
| groups |
| his |
| history |
| history_log |
| history_str |
| history_text |
| history_uint |
| host_discovery |
| host_inventory |
| hostmacro |
| hosts |
| hosts_groups |
| hosts_templates |
| housekeeper |
| httpstep |
| httpstepitem |
| httptest |
| httptestitem |
| icon_map |
| icon_mapping |
| ids |
| images |
| interface |
| interface_discovery |
| item_application_prototype |
| item_condition |
| item_discovery |
| items |
| items_applications |
| maintenances |
| maintenances_groups |
| maintenances_hosts |
| maintenances_windows |
| mappings |
| media |
| media_type |
| opcommand |
| opcommand_grp |
| opcommand_hst |
| opconditions |
| operations |
| opgroup |
| opinventory |
| opmessage |
| opmessage_grp |
| opmessage_usr |
| optemplate |
| problem |
| problem_tag |
| profiles |
| proxy_autoreg_host |
| proxy_dhistory |
| proxy_history |
| regexps |
| rights |
| screen_user |
| screen_usrgrp |
| screens |
| screens_items |
| scripts |
| service_alarms |
| services |
| services_links |
| services_times |
| sessions |
| slides |
| slideshow_user |
| slideshow_usrgrp |
| slideshows |
| sysmap_element_url |
| sysmap_url |
| sysmap_user |
| sysmap_usrgrp |
| sysmaps |
| sysmaps_elements |
| sysmaps_link_triggers |
| sysmaps_links |
| task |
| task_close_problem |
| timeperiods |
| trends |
| trends_uint |
| trigger_depends |
| trigger_discovery |
| trigger_tag |
| triggers |
| users |
| users_groups |
| usrgrp |
| valuemaps |
+----------------------------+
129 rows in set (0.01 sec)
mysql> 查询数据库sessions表条目数量
mysql> select count(*) from sessions;
+----------+
| count(*) |
+----------+
| 23143363 |
+----------+
1 row in set (10.28 sec)下面这条命令是按sessions 表中 lastaccess 字段的时间 删除 2019/10/31 12:0:00 之前的所有条目
mysql> delete from sessions where FROM_UNIXTIME(lastaccess)>FROM_UNIXTIME(1572494400); （2019/10/31 12:0:0）我本意是想删除2019/10/31 12:0:0 以前的数，最后删除后发现 还有2千多万条，想想是不对的，select 一下发现 把10月31号之后的记录删除了。我擦擦。。。。
修改语句如下：
mysql> delete from sessions where FROM_UNIXTIME(lastaccess)<FROM_UNIXTIME(1572494400); （2019/10/31 12:0:0）
验证如下：
mysql> select * from sessions limit 10 ;mysql> select count(*) from sessions;
+----------+
| count(*) |
+----------+
| 4178 |
+----------+
1 row in set (7.01 sec)
mysql> 完美搞定点击用户hang住的问题。
追加一些其它的查询
切换到 information_schema数据库
mysql> use information_schema;
查询mysql数据最大的10张表
mysql> select TABLE_SCHEMA,table_name,table_rows,ENGINE,DATA_LENGTH,MAX_DATA_LENGTH,DATA_FREE from tables order by table_rows desc limit 10;
+---------------+--------------+------------+--------+-------------+-----------------+-------------+
| TABLE_SCHEMA | table_name | table_rows | ENGINE | DATA_LENGTH | MAX_DATA_LENGTH | DATA_FREE |
+---------------+--------------+------------+--------+-------------+-----------------+-------------+
| haiwai_zabbix | history_uint | 438673983 | InnoDB | 37073469440 | 0 | 145752064 |
| haiwai_zabbix | history | 227527074 | InnoDB | 21833465856 | 0 | 114294784 |
| haiwai_zabbix | trends_uint | 100126348 | InnoDB | 7990231040 | 0 | 93323264 |
| zabbix_server | history | 58115887 | InnoDB | 3786424320 | 0 | 0 |
| haiwai_zabbix | trends | 37399078 | InnoDB | 3267461120 | 0 | 26214400 |
| haiwai_zabbix | history_log | 34415220 | InnoDB | 18999181312 | 0 | 19042140160 |
| haiwai_zabbix | sessions | 24138136 | InnoDB | 3531407360 | 0 | 504365056 |
| zabbix_test | trends_uint | 21860377 | InnoDB | 1386217472 | 0 | 0 |
| haiwai_zabbix | history_str | 20434046 | InnoDB | 1628454912 | 0 | 82837504 |
| zabbix_server | history_uint | 17969842 | InnoDB | 1420836864 | 0 | 0 |
+---------------+--------------+------------+--------+-------------+-----------------+-------------+
10 rows in set, 48 warnings (12.80 sec)
mysql> 查看表字段
mysql>desc 表名
mysql> desc history_unit;
mysql> desc history_uint ;
+--------+---------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------+---------------------+------+-----+---------+-------+
| itemid | bigint(20) unsigned | NO | MUL | NULL | |
| clock | int(11) | NO | | 0 | |
| value | bigint(20) unsigned | NO | | 0 | |
| ns | int(11) | NO | | 0 | |
+--------+---------------------+------+-----+---------+-------+
4 rows in set (0.00 sec)
mysql> 查history_unit表中10行的条目
mysql> select * from history_uint limit 10;
+--------+------------+-------+-----------+
| itemid | clock | value | ns |
+--------+------------+-------+-----------+
| 31558 | 1500590724 | 1 | 50697203 |
| 33718 | 1500590724 | 1 | 61039023 |
| 24456 | 1500590724 | 0 | 292227168 |
| 31559 | 1500590725 | 1 | 51844995 |
| 33719 | 1500590725 | 1 | 66514533 |
| 41519 | 1500590725 | 1 | 70626763 |
| 42059 | 1500590725 | 1 | 278047684 |
| 31560 | 1500590726 | 1 | 63953848 |
| 33720 | 1500590726 | 1 | 71027961 |
| 31561 | 1500590727 | 1 | 64017492 |
+--------+------------+-------+-----------+
10 rows in set (0.00 sec)
mysql>